1. Field of the Invention
The present invention relates to a work conveying system for a clean room and more particularly to a work conveying system which conveys a workpiece to various processing stations in a production line within a clean room for the production of, for example, semiconductor components, liquid crystal display panels, medical supplies, chemicals, and processed foods.
2. Description of the Prior Art
In manufacture of a semiconductor integrated circuit or a liquid crystal display panel, deposition of dust must be avoided. It is desirable that medical supplies, chemicals, and processed foods be produced in a sterile hygienic environment. Therefore, in a wide variety of fields, intra-clean room production lines are utilized.
The present applicant has previously invented a work conveying system (see Japanese Patent Laid Open No. 2000-243808), which system is provided with drive means able to arbitrarily move a work holding means in three dimensions in an upper ceiling space within a clean room. In this work conveying system, a pair of horizontal fixed guide rails are laid in parallel in the ceiling space and one or plural horizontal traveling guide rails are mounted between the paired fixed guide rails for travel along the fixed guide rails. Also, a travel body is mounted for travel along the traveling guide rail(s), and a horizontal moving means is provided by the combination of the fixed guide rails, the traveling guide rail(s) and the travel body. Further, the travel body is provided with a vertical moving means for raising and lowering the work holding means. Thus, three-dimensional movement/conveyance is provided by the combination of the vertical moving means and the horizontal moving means.
FIGS. 10(A), 10(B), 11(A) and 11(B) show such a vertical moving means 013, in which FIG. 10(A) is a front view showing a raised state of the vertical moving means, FIG. 10(B) is a side view in vertical section, FIG. 11(A) is a front view showing a lowered state thereof, and FIG. 11(B) is a side view in vertical section. As shown in these figures, the vertical moving means 013 is an articulated arm having three arm elements 016-018. With pivotal movements of a first start-end arm element 016, a second arm element 017, and a third (terminal-end) arm element 018, a work holding means 011 fixed to the third (terminal-end) arm element 018 is moved up and down on a vertical line. The work holding means 011 delivers a workpiece (e.g., a hermetically sealed container) to each of various processing apparatuses. As shown in FIGS. 10(B) and 11(B), the articulated arm has the arm elements 016-018 stacked in multiple stages.
The pivotal movements of the arm elements 016-018 are respectively driven by a motor 021a disposed within a body 015, a motor 021b disposed within the first start-end arm element 016, and a motor 021c disposed within the second arm element 017. Though not shown in detail, the interiors of the arm elements 016-018 and the interior of the body 015 are in communication and are under a negative pressure so that dust generated in those interiors is removed in one direction.
With the above-described work conveying system, an area for work conveyance is not required on the floor surface of the clean room and the interior of the clean room can be more effectively utilized. Therefore, for the same equipment, the space required in the clean room can be reduced and it is possible to reduce the equipment cost and operation cost of the clean room. Moreover, the location and orientation of apparatus such as processing chambers installed within the clean room are not restricted and it is possible to select an optimal arrangement. Also in the case of adding a new apparatus such as a processing chamber or in the case of changing the arrangement of items such as processing chambers, it is possible to freely select their arrangement and orientation. Thus, it is also possible to reduce the cost of changing arrangement of or increasing the number of items of apparatus such as processing chambers. Further, it is possible to move the work holding means 011 linearly from one position to another position, whereby the work efficiency in the clean room is improved.
However, in the above-described work conveying system, a torque load based on arm weight is imposed on the mounting portion for mounting to the horizontal moving means and deflection caused by extension of the articulated arm is significant. Further, in the articulated arm of this structure, the pivotal movement of the first start-end arm element 016 relative to the horizontal moving means is performed by operation of a motor 021a provided on the horizontal moving means (travel body 015) side and thus this structure is difficult to seal. In addition, motors 021a-021c are used as dedicated drive sources for pivotal movements of the first to third arm elements 016-018, respectively, and such multiple drive sources are apt to generate dust.
It is an object of the present invention to solve the above-mentioned problems of the conventional work conveying system and to provide a work conveying system which eliminates gravitational deflection induced upon extension of the articulated arm in the vertical moving means, permits the work holding means to deliver a workpiece to each processing apparatus without dislocation, permits smooth extension and contraction of the articulated arm, permits the vertical moving means to be folded compactly when conveying a workpiece horizontally, thereby minimizing the disturbance of air flow, and which is easily sealed.
It is another object of the present invention to provide a work conveying system which, in the case of workpieces in the form of wafers or reticles, can convey the wafers or reticles each individually and rapidly to a predetermined processing apparatus and can thereby improve the working efficiency.
For solving the foregoing problems, in one aspect of the present invention, there is provided a work conveying system comprising a work holding means for holding a workpiece, a horizontal moving means for moving the work holding means horizontally in an upper ceiling space within a clean room, and a vertical moving means provided in the horizontal moving means and formed as an articulated arm, the articulated arm being adapted to extend and contract, thereby causing the work holding means to move up and down, the workpiece thereby being conveyed to the plural items of apparatus while circulating among the processing stations within the clean room, wherein plural arm elements of the articulated arm are overlapped and connected together at alternating end portions, and the articulated arm is extended and contracted with pivotal movements of the arm elements.
With the above-described first aspect of the invention there is no fear of centroid deviation of the articulated arm and the weight balance of the entire arm is stable, with little gravitational deflection, even upon extension (descent of the vertical moving means). Consequently, it becomes possible for the work holding means to deliver a workpiece to each of various processing apparatuses without dislocation, the extension and contraction of the articulated arm being performed smoothly, and when conveying a work horizontally, the vertical moving means can be folded compactly to minimize the disturbance of air flow. Further, there is no torque based on the weight of the entire arm and the workpiece weight, thus permitting stable conveyance of a workpiece horizontally.
In a second aspect the present invention provides a work conveying system comprising work holding means for holding a workpiece, horizontal moving means for moving the work holding means horizontally and located in an upper ceiling space within a clean room, and an articulated arm, serving as vertical moving means and provided on the horizontal moving means. The articulated arm extends and contracts to thereby cause the work holding means to move up and down, allowing the work to be transferred between the work holding means and each of plural items of processing apparatus, while the workpiece is circulated among the different items of processing apparatus within the clean room. The articulated arm has three or more arm elements, a single drive, and a predetermined pivoting ratio among the arm elements. The articulated arm is extended and contracted linearly by operation of the drive source and consequent pivotal movements of the arm elements, so that by a combined use of a single drive source and three or more arm elements which are interlocked with one another, smooth motion free of impact is ensured.
A third aspect of the present invention provides, in combination with the above-described first aspect, a work conveying system wherein the vertical drive means, constituted by an articulated arm having three or more arm elements, has a single drive source and a predetermined pivoting ratio among the arm elements, and the articulated arm is extended and contracted by operation of the drive source and by consequent pivotal movements of the arm elements. By a combined use of a single drive source and three or more arm elements that are interlocked with one another, there is obtained a smooth impact-free motion.
In a fourth aspect the present invention provides, in combination with the above-described first or second aspect, mounting of the horizontal moving means in the upper ceiling space within the clean room for movement in an arbitrary horizontal plane. The work holding means is also movable in an arbitrary horizontal plane in the upper ceiling space within the clean room, so that the location and orientation of items of processing apparatus, such as processing chambers installed within the clean room, are not restricted and it is possible to select an optimal arrangement. Moreover, also in the case of adding a new item of apparatus, such as a new processing chamber, or in the case of changing the arrangement of the apparatus, it is possible to freely select their arrangement and orientation and hence the cost for changing the arrangement of or adding to the apparatus is reduced. Further, it is possible to move the work holding means linearly from one position to another position and therefore the work processing efficiency within the clean room is improved.
In a fifth aspect the present invention provides, in combination with the above second aspect, pivotal movement of a first start-end arm of the vertical moving means, relative to the horizontal moving means, is driven by a motor disposed on the first arm element. This construction provides for sealing of dust generated from a single drive source (the motor) and the dust generated from the pivoting structure, all on the arm side. Further, by utilizing an empty space, i.e. the internal space within the first arm element, it is possible to accommodate the motor which serves as the sole drive source, thus affording a work conveying system of a compact structure.
In a sixth aspect the present invention provides, in combination with the above first or second aspect, a work conveying system wherein the arm elements of the articulated arm are hollow and the internal spaces within the arm elements are intercommunicated and evacuated to a negative pressure. With this structure discharge of generated dust from the internal space of each of the arm elements is simplified, the amount of dust leaking into the clean room is greatly decreased, and it becomes easy to maintain the clean room at a required degree of cleanliness.
In a seventh aspect the present invention provides, in combination with the above first or second aspect, a work conveying system wherein the work holding means is provided with a work rotation drive unit so that the work can be rotated in a horizontal plane. This work rotation drive unit, in addition to facilitating conveyance of the work in three dimensions, provides a rotational direction/posture control for the work in a horizontal plane and accurate rotational positioning in loading the work, thus fulfilling requirements for high degree of accuracy in a work conveying system.
The present invention may also include a hermetically sealed work container held by the work holding means. Plural wafers or reticles may be accommodated in the hermetically sealed work container and in this state can be conveyed within the clean room, so that it is possible to easily attain the high-degree of cleanliness required for such workpieces.
Alternatively, the work holding means may hold a single workpiece, such as a wafer or a reticle, directly.
Further, the directly held workpiece may bear an identification mark indicating the processing steps to which the workpiece is to be subjected. In this case the apparatus of the present invention further includes a detector for reading the identification mark. In directly holding a single workpiece, the detector on the work holding means reads the identification mark and transmits a signal to a controller in the work conveying system, whereby the work conveying system can convey the workpiece rapidly to each processing apparatus in a predetermined sequence for predetermined working, within the three-dimensional space of a clean room. Consequently, the working efficiency of the work conveying system is improved to a remarkable extent.
Alternatively, the detector for detecting identification marks on workpieces may be disposed at a fixed position within the clean room. The detector reads the identification mark affixed to the workpiece upon arrival of the workpiece at the installed position of the detector and then transmits a signal to a controller in the work conveying system, whereby the work conveying system can convey a single workpiece to each processing apparatus rapidly and in a predetermined sequence for predetermined processings. Consequently, the working efficiency of the work conveying system is greatly improved.